During tracheal surgery it is important to maintain both adequate ventilation and oxygenation. However, standard technology for gas ventilation during open tracheal surgery poses several problems. First, proper ventilation and oxygenation requires large volumes of gas to be introduced. To facilitate introduction of sufficient volumes of gas, large diameter endotracheal or endobronchial tubes are often used. These large diameter tubes interfere with the surgeon's access to the trachea. Additionally, these large diameter tubes can be hazardous to the patient because of the risk of damage or trauma to the bronchial or tracheal wall due to potential impact with the tube.
High pressure jet air can be used with smaller diameter tubes to introduce an amount of air into the trachea equivalent to that produced by a much larger diameter tube. Various devices have been used during anesthesia to provide proper ventilation and oxygenation while simultaneously attempting to provide optimal unobstructed surgical access. The force exerted by a focused stream of exiting high-pressure jet gas against the wall of the carina or trachea may, however, cause possible harm to the patient. In addition, because of the instability of a small diameter catheter in the tracheal lumen there is potential for the distal end of the catheter to move or whip about as the high pressure gas is discharged from the tip of the catheter.
Previous efforts of using high-frequency or high-pressure ventilation through relatively small diameter catheters have resulted in devices which cause a focused high-pressure stream of gas exiting at the distal tip. Completely open orifices at the distal end of ventilation catheters are unacceptable due to this strong unidirectional gas flow at the catheter tip and the potential injury to the patient.
A device called the BEN-JET catheter, described by Dr. Bruce Benjamin et al., Anaesth. Intens. Care, 7:258-263 (1979), was developed to solve the potential injury problems associated with jet ventilation catheters. The BEN-JET is now manufactured by Tuta Laboratories Pty. Ltd. of Sydney, Australia. The BEN-JET catheter employs the use of four soft plastic "petals" at the distal end. The purpose of these petals is to help maintain the distal end of the ventilation catheter in a central portion of the trachea and thereby prevent trauma to the tracheal wall and ensure even distribution of ventilation gas. In the BEN-JET catheter, the petals fold back toward the proximal end of the catheter and expose an unobstructed orifice at the distal end of the catheter tube. The high pressure gas exits this orifice directly into the trachea. Because the path of the gas stream is unobstructed, the tracheal wall is exposed to the full force of the high pressure stream. The BEN-JET device, therefore, has the disadvantage of exposing the tracheal wall to the full force of the jet ventilation gas as it exits the catheter in a unified stream. This disadvantage is common in the prior art. It is a general object of this invention to provide an apparatus having a structure which overcomes this disadvantage by protecting the wall of the trachea from the potential injury created by the strong force of exiting high-pressure jet gas or by the possible whipping or lashing also caused by the exiting gas.
The unique construction of the invention provides for several prominent advantages over the prior art. First, the catheter outflow orifice is housed in a plurality of outwardly biased flanges terminating in a distal tip which divert the unidirectional flow of the high-pressure oxygen jet stream and cause the gas stream to disperse through gaps between the flanges, thereby reducing the force of the gas against the tracheal wall. Second, the catheter has retractable flanges which minimize damage to the trachea or bronchi during insertion or withdrawal of the catheter. Third, the catheter has a flexible internal stylette allowing the catheter to be bent into different shapes for ease of insertion and withdrawal. Fourth, the flexible stylette is hollow and allows for insertion or change of the catheter over a flexible, metal guide wire. In addition, the catheter may be of a longer length than prior art catheters allowing passage into the distal airways from an oral intubation.